The reasons of affecting the SIC heater rod usage life
SIC heater is common electric heating elements of thermo equipment, with high temperature, oxidation resistance, corrosion resistance features , the temperature up to 1500 ℃, is the heating element of the high temperature electric furnace, laboratory furnace. Generally , the life of SIC heater is quite long, but some of our daily operation practices and usage will affect the life of the SIC heater and depend on the following 4 reasons:
A. the furnace atmosphere
In the process of high temperature electric furnace work burned a large number of chemical substances, common water, hydrogen, nitrogen, sulfur and other gases and molten aluminum, alkali, salt, molten metal, metal oxide, these substances and the heating state of SIC heater reaction, there will be corrosion and oxidation of silicon carbon rods have a certain impact.
B. the surface load
The surface load density refers to the maximum power that can be carried by the surface area of the silicon carbide rod. Surface load density is equal to the rated power (W) / heating surface area (cm2)
Practice has proved that: surface load density and silicon carbide surface temperature has a great relationship between the load density of the heating surface temperature and the furnace temperature difference is also large, resulting in silicon carbide surface temperature rise, resistance growth, silicon carbide Life will be reduced. Therefore, to extend the life of silicon carbon rods, control the silicon carbide surface temperature and surface load density is essential.
C. the connection method of wire
SIC heater are generally used in combination of string and parallel wires. It is recommended to use two sets in series as a group after multiple groups in parallel. Especially when the furnace temperature exceeds 1350 ℃ must be parallel. Three-phase wiring is recommended for open triangular wiring. If the resistance of silicon carbon rods are different, the high resistance of silicon carbide rods in series is more concentrated, which can lead to the rapid increase of the resistance of a silicon carbide rod.
D. the pattern of the furnace operation
Silicon carbon rods are used in continuous electric furnaces and intermittent electric furnaces. The service life of silicon carbon rods and the operation mode of kiln are also greatly related. Generally speaking, the life of silicon carbon rods in continuous electric furnace is long. Silicon carbon rods in the course of the use of surface oxidation of silicon dioxide film, prolonged use of the silica film to increase the silicon carbide rod resistance also increases. Silica film in the crystallization of the critical point (270 ℃) near the abnormal expansion, contraction. Due to the intermittent use of intermittent kiln in the temperature of the total floating up and down, so repeatedly broken silica film to accelerate oxidation. So the furnace temperature dropped to room temperature is often a sharp increase in resistance.
To extend the life of silicon carbide rods in terms of the entire heat treatment equipment is also very useful, and indirectly improve the efficiency of the furnace, so the extension of the use of silicon carbide rod is also very important, the user can not ignore it in the course of the usage.